I've made a mistake, (I'm pretty sure), by combining a light switch with a built in speaker volume control in a double gang box. It all works fine but I now realize the risks of this maneuver. Question is, Do they make a dual voltage old work box? and if so, is that what I need to use?
Oh it isn't the worst thing on the planet. When you combine premise wiring from the utility with low voltage they make divider plates (partitions) to separate two compartments in the device box. I couldn't find a good image.
Some examples below of different methods
" One nice thing about the NEC articles ... you have lots of choices"